Method and apparatus for downlink control physical structure in reduced latency operation

ABSTRACT

A method and apparatus can provide for signaling of a higher layer message. A higher layer message from a base station indicating to monitor a control channel using demodulation reference signals in a shortened transmission time interval in a subframe can be received. A first control channel candidate in the shortened transmission time interval can be attempted to be decoded, where the first control channel candidate comprises a first shortened control channel element spanning a first set of shortened resource element groups in a frequency domain using a first demodulation reference signal on a first antenna port, where a first precoder applies to all demodulation reference signal resource elements in the first set of shortened resource element groups. A second control channel candidate in the shortened transmission time interval can be attempted to be decoded.

BACKGROUND 1. Field

The present disclosure is directed to a method and apparatus forsignaling on a wireless network. More particularly, the presentdisclosure is directed to a method and apparatus for downlink controlphysical structure in reduced latency operation.

2. Introduction

Presently, 5th Generation (5G) New Radio (NR) wireless systems,abbreviated 5G NR, offer improved wireless network technologies. 5G NRincludes such technologies as millimeter wave bands, such as 26, 28, 38,and 60 GHz and can offer theoretical throughput as high as 20 gigabitsper second, with median bandwidth being approximately 3.5 gigabits. 5GNR can utilize Multiple Input Multiple Output (MIMO), for example 64-256antennas, to provide up to ten times the performance of 4^(th)Generation (4G) networks. In current 3rd Generation Partnership Project(3GPP) Long Term Evolution (LTE), time-frequency resources can bedivided into subframes where each 1 ms subframe can comprise two 0.5 msslots and each slot, such as with normal Cyclic Prefix (CP) duration,can comprise 7 Single-Carrier Frequency Division Multiple Access(SC-FDMA) symbols in time domain in uplink (UL) and 7 OrthogonalFrequency Division Multiplexing (OFDM) symbols in time domain indownlink (DL). In frequency domain, resources within a slot can bedivided into Physical Resource Blocks (PRBs), where each resource blockcan span twelve contiguous subcarriers.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which advantages and features of thedisclosure can be obtained, a description of the disclosure is renderedby reference to specific embodiments thereof which are illustrated inthe appended drawings. These drawings depict only example embodiments ofthe disclosure and are not therefore to be considered to be limiting ofits scope. The drawings may have been simplified for clarity and are notnecessarily drawn to scale.

FIG. 1 is an example block diagram of a system, according to a possibleembodiment;

FIG. 2 illustrates example agreed Downlink (DL) short Transmit TimeInterval (sTTI) patterns, according to a possible embodiment;

FIG. 3 illustrates an example sTTI DL pattern, according to a possibleembodiment;

FIG. 4 illustrates another example sTTI DL pattern, according to apossible embodiment;

FIG. 5 illustrates an example short Resource Block Group (sRBG),according to a possible embodiment;

FIG. 6 illustrates another example sRBG, according to a possibleembodiment;

FIG. 7 illustrates yet another example sRBG, according to a possibleembodiment;

FIG. 8 illustrates an example illustration of 1-symbol lengthCell-specific Reference Signals (CRS)-based short Physical DownlinkControl Channel (sPDCCH), according to a possible embodiment;

FIG. 9 illustrates an example 3-symbol sTTI, according to a possibleembodiment;

FIG. 10 illustrates an example illustration showing a DemodulationReference Signal (DMRS) sharing example between DMRS-based sPDCCH andshort Physical Downlink Shared Channel (sPDSCH), according to a possibleembodiment;

FIG. 11 illustrates another DMRS sharing example between DMRS-basedsPDCCH and sPDSCH, according to a possible embodiment;

FIG. 12 illustrates an example sCCE structure, according to a possibleembodiment;

FIG. 13 illustrates another example sCCE structure, according to apossible embodiment;

FIG. 14 illustrates example sRBGs where two sRBGs and can overlap withPhysical Broadcast Channel (PBCH) resources, according to a possibleembodiment;

FIG. 15 illustrates an example of different control resource mapping,according to a possible embodiment;

FIG. 16 illustrates a similar example to the example shown in FIG. 15but with a single sRBG of twelve (12) RBs, according to a possibleembodiment;

FIG. 17 illustrates an example flowchart illustrating operation of anapparatus such as a user equipment, according to a possible embodiment;

FIG. 18 illustrates another example flowchart illustrating operation ofan apparatus such as the user equipment, according to a possibleembodiment;

FIG. 19 illustrates an example flowchart illustrating operation of anapparatus such as a network entity, according to a possible embodiment;

FIG. 20 illustrates another example flowchart illustrating operation ofan apparatus such as the network entity, according to a possibleembodiment; and

FIG. 21 illustrates an example block diagram of an apparatus, accordingto a possible embodiment.

DETAILED DESCRIPTION

Embodiments provide a method and apparatus for downlink signaling of ahigher layer message. According to a possible embodiment, a higher layermessage from a base station indicating to monitor a control channelusing demodulation reference signals in a shortened transmission timeinterval in a subframe can be received, where the higher layer can behigher than a physical layer, and where the shortened transmission timeinterval can be shorter than a subframe-length transmission timeinterval. A first control channel candidate in the shortenedtransmission time interval can be attempted to be decoded, where thefirst control channel candidate can comprise a first shortened controlchannel element that can span a first set of shortened resource elementgroups in a frequency domain using a first demodulation reference signalon a first antenna port, where a first precoder can apply to alldemodulation reference signal resource elements in the first set ofshortened resource element groups, where the shortened control channelelement can correspond to the shortened transmission time interval. Asecond control channel candidate in the shortened transmission timeinterval can be attempted to be decoded, where the second controlchannel candidate can comprise a second shortened control channelelement that can span a second set of shortened resource element groupsin the frequency domain using a second demodulation reference signal ona second antenna port, where a second precoder can apply to alldemodulation reference signal resource elements in the second set ofshortened resource element groups. A first shortened resource elementgroup of the first set of shortened resource element groups can occupy afirst set of resource elements in a given resource block in a firstorthogonal frequency division multiplexing symbol of the shortenedtransmission time interval and a second shortened resource element groupof the second set of shortened resource element groups can occupy asecond set of resource elements, in the given resource block in a secondorthogonal frequency division multiplexing symbol of the shortenedtransmission time interval, where the first orthogonal frequencydivision multiplexing symbol can be different from the second orthogonalfrequency division multiplexing symbol.

Embodiments provide another method and another apparatus for downlinksignaling of a higher layer message. According to a possible embodiment,a higher layer message indicating to monitor a control channel usingdemodulation reference signals in a shortened transmission time intervalin a subframe can be transmitted by a device, where the higher layer canbe higher than a physical layer, and where the shortened transmissiontime interval can be shorter than a subframe-length transmission timeinterval. A first control channel candidate in the shortenedtransmission time interval can be transmitted, where the first controlchannel candidate can comprise a first shortened control channel elementthat can span a first set of shortened resource element groups in afrequency domain using a first demodulation reference signal on a firstantenna port, where a first precoder can apply to all demodulationreference signal resource elements in the first set of shortenedresource element groups, where the shortened control channel element cancorrespond to the shortened transmission time interval. A second controlchannel candidate in the shortened transmission time interval can betransmitted, where the second control channel candidate can comprise asecond shortened control channel element that can span a second set ofshortened resource element groups in the frequency domain using a seconddemodulation reference signal on a second antenna port, where a secondprecoder can apply to all demodulation reference signal resourceelements in the second set of shortened resource element groups. A firstshortened resource element group of the first set of shortened resourceelement groups can occupy a first set of resource elements in a givenresource block in a first orthogonal frequency division multiplexingsymbol of the shortened transmission time interval and a secondshortened resource element group of the second set of shortened resourceelement groups can occupy a second set of resource elements, in thegiven resource block in a second orthogonal frequency divisionmultiplexing symbol of the shortened transmission time interval, wherethe first orthogonal frequency division multiplexing symbol can bedifferent from the second orthogonal frequency division multiplexingsymbol.

Embodiments provide another method and another apparatus for downlinksignaling of a higher layer message. According to a possible embodiment,a higher layer message from a base station can be received, formonitoring control channel candidates in at least one shortenedtransmission time interval in a subframe and set of resource blockscorresponding to control channel candidates in the at least oneshortened transmission time interval, where the higher layer can behigher than a physical layer, and where the shortened transmission timeinterval can be shorter than a subframe-length transmission timeinterval. Whether at least one resource block of the set of resourceblocks at least partially overlaps with a broadcast control channel orsignal can be determined. Control resource elements used fortransmission of a control channel candidate can be based on thedetermination whether the at least one resource block of the set ofresource blocks at least partially overlaps with the broadcast controlchannel or signal. The control channel candidate in the at least oneshortened transmission time interval according to the determined controlresource elements can be attempted to be decoded, wherein the controlchannel candidate comprises a shortened control channel element spanninga set of shortened resource element groups in a frequency domain.

Embodiments provide another method and another apparatus for downlinksignaling of a higher layer message. According to a possible embodiment,a higher layer message for monitoring control channel candidates in atleast one shortened transmission time interval in a subframe and set ofresource blocks corresponding to control channel candidates in the atleast one shortened transmission time interval can be transmitted. Thehigher layer can be higher than a physical layer. An shortenedtransmission time interval can be shorter than a subframe-lengthtransmission time interval. At least one resource block of the set ofresource blocks at least can partially overlap with a broadcast controlchannel or signal. Control resource elements used for transmission of acontrol channel candidate based on the at least one resource block ofthe set of resource blocks at least partially overlapping in frequencywith a broadcast control channel or signal can be determined. Thecontrol channel candidate in the at least one shortened transmissiontime interval according to the determined control resource elements canbe transmitted. The control channel candidate can comprise a shortenedcontrol channel element spanning a set of shortened resource elementsgroups in a frequency domain.

FIG. 1 illustrates an example block diagram of a system 100, accordingto a possible embodiment. The system 100 can include a User Equipment(UE) 110, at least one of network entities 120 and 125, such as a basestation, and a network 130. The UE 110 can be a wireless wide areanetwork device, a user device, wireless terminal, a portable wirelesscommunication device, a smartphone, a cellular telephone, a flip phone,a personal digital assistant, a personal computer, a selective callreceiver, an Internet of Things (IoT) device, a tablet computer, alaptop computer, or any other user device that is capable of sending andreceiving communication signals on a wireless network. The at least oneof network entities 120 and 125 can be wireless wide area network basestations, can be NodeBs, can be enhanced NodeBs (eNBs), can be New RadioNodeBs (gNBs), such as 5G NodeBs, can be unlicensed network basestations, can be access points, can be base station controllers, can benetwork controllers, can be Transmission/Reception Points (TRPs), can bedifferent types of base stations from each other, and/or can be anyother network entities that can provide wireless access between a UE anda network. A higher layer message(s) 140 can include various signalstransmitted from the network entity 120 and various signals received bythe UE 110 described herein.

The network 130 can include any type of network that is capable ofsending and receiving wireless communication signals. For example, thenetwork 130 can include a wireless communication network, a cellulartelephone network, a Time Division Multiple Access (TDMA)-based network,a Code Division Multiple Access (CDMA)-based network, an OrthogonalFrequency Division Multiple Access (OFDMA)-based network, a Long TermEvolution (LTE) network, a 3rd Generation Partnership Project(3GPP)-based network, a satellite communications network, a highaltitude platform network, the Internet, and/or other communicationsnetworks. In a possible embodiment, the network entity 120 and the UE110 can be included in a cell 135, the network entity 125 can beincluded in another cell 155, and the network entities 120 and 125 canbe coupled via the network 130.

In operation, the UE 110 can communicate with the network 130 via thenetwork entity 120. For example, the UE 110 can send and receive controlsignals on a control channel and user data signals on a data channel.

In current LTE systems, resources can be assigned using a 1 ms minimumtransmission time interval (TTI) when data is available, referred to asdynamic scheduling. Within each scheduled TTI, in UL, a UE 110 cantransmit data over a Physical Uplink Shared Channel (PUSCH) in PRB-pairsindicated by an uplink grant to the UE 110 that schedules the datatransmission. In DL, the network entity 120 can transmit data over aPDSCH in PRB-pairs indicated by a DL grant/assignment. The UL grantand/or DL assignment information can be provided to the UE 110 in acontrol channel, referred to as a PDCCH or Enhanced PDCCH (EPDCCH). The(E)PDCCH channel can carry the control information about the data beingtransmitted on the current subframe and the information about theresources that the UE 110 needs to use for uplink data.

There can be two types of downlink physical layer control signaling forthe purpose of dynamic scheduling. One type of downlink physical layercontrol signaling for the purpose of dynamic scheduling can be PDCCHwhere the control signaling from the network entity 120 can be receivedby the UE 110 in the first, first two, or first three, or first foursymbols of a subframe subsequently referred to as control symbols. Theremaining symbols in the subframe, following the control symbols, cantypically be used for receiving user data. User data can be received bythe UE 110 on the PDSCH, and in select Resource Blocks (RBs) of thePDSCH occupying either in the entire carrier bandwidth or a portion ofit.

The set of PDCCH candidates to monitor are defined in terms of searchspaces, where a search space S_(k) ^((L)) at aggregation levelL∈{1,2,4,8} can be defined by a set of PDCCH candidates. For eachserving cell on which PDCCH can be monitored, the Control ChannelElements (CCEs) corresponding to a PDCCH candidate of the search spaceS_(k) ^((L)) can be given by a formula taking parameters including totalnumber of CCEs in the control region of subframe, such as derived fromreduction of Physical Control Format Indicator Channel (PCFICH) andPhysical channel Hybrid Admission Request (HybridARQ) Indicator Channel(PHICH) resources, an aggregation level, a number of PDCCH candidates tomonitor in the given search space, and a slot number within the radioframe.

A physical control channel can be transmitted on an aggregation of oneor several consecutive CCEs, where a control channel element cancorrespond to 9 resource element groups. Each CCE can be equivalent to36 resource elements (REs). One CCE can be the minimum PDCCH allocationunit.

The number of resource-element groups not assigned to PCFICH or PHICHcan be N_(REG). The CCEs available in the system 100 can be numberedfrom 0 to N_(CCE)−1, where N_(CCE)=└N_(REG)/9┘. A PDCCH can consist of nconsecutive CCEs and may only start on a CCE fulfilling i mod n=0, wherei can be the CCE number.

Another type of downlink physical layer control signaling for thepurpose of dynamic scheduling can be EPDCCH. For each serving cell,higher layer signaling including the higher layer message(s) 140 canconfigure the UE 110 with one or two EPDCCH-PRB-sets for EPDCCHmonitoring. The PRB-pairs corresponding to an EPDCCH-PRB-set can beindicated by higher layers. Each EPDCCH-PRB-set can consist of a set ofenhanced control channel elements (ECCEs) numbered from 0 toN_(ECCE,p,k)−1 where N_(ECCE,p,k) can be the number of ECCEs inEPDCCH-PRB-set p of subframe k. Each EPDCCH-PRB-set can be configuredfor either localized EPDCCH transmission or distributed EPDCCHtransmission.

For each serving cell, the subframes in which the UE 110 monitors EPDCCHUE-specific search spaces can be configured by higher layers. The UE 110can monitor a set of (E)PDCCH candidates for control information, wheremonitoring can imply attempting to decode each of the (E)PDCCH decodingcandidates in the set according to the monitored Downlink ControlInformation (DCI) formats. The set of (E)PDCCH candidates to monitor canbe defined in terms of (E)PDCCH search spaces.

To reduce latency of communication in LTE, various solutions are beingstudied. For example, an approach envisioned for future LTE systems caninclude use of a shorter minimum TTI, such as shorter than 1 ms, inUL/DL. Using a sTTI, such as a minimum sTTI, can allow the UE 110 tosend/receive data using reduced latency when compared to current LTEsystems. In addition, acknowledging each (or a group containing few)sTTI(s) leading to faster, as compared to using 1 ms TTI, acknowledgingdata can help in some applications, such as Transmission ControlProtocol (TCP), during slow-start phase for users in good channelconditions. For example, in the TCP slow-start phase for DLcommunication, the network 130-UE 110 link capacity for the UE 110 ingood channel condition can support more data, but the network 130 sendsa smaller amount of data because the network 130 can be waiting toreceive the acknowledgment for the previously sent data due to the TCPslow-start phase. Therefore, faster acknowledgments, such as a result ofusing shorter TTI length, can enable the network 130 to better utilizethe available network 130-UE 110 link capacity.

The currently supported sTTI configurations within a subframe can beeither (A) a combination of 6 sTTIs each composed of two or three, suchas OFDM symbols in DL or SC-FDMA symbols in UL, symbols or (B) two 0.5ms-length sTTIs. For example, scheduling UE 110 transmission over ansTTI length of 0.5 ms, such as PUSCH scheduled using a PRB spanning a0.5 ms in a 1 ms subframe, or scheduling UE 110 transmission over ansTTI length of ˜140 us, such as PUSCH scheduled using a shortened PRBspanning two SC-FDMA symbols within a slot in a subframe, would not onlyreduce time taken to start/finish transmitting a data packet, but alsopotentially reduce round trip time for possible Hybrid Automatic RepeatRequest (HARQ) retransmissions related to that data packet.

The PDCCH channel can carry control information about data beingtransmitted on a current subframe and information about resources whichthe UE 110 needs to use for the uplink data. The UE 110 can decode it ifit wants to send some data or receive something. For reduced latency ashortened Physical Downlink Control Channel (sPDCCH) can be defined toplay a similar role in an sTTI, or a group of sTTIs. For PDCCH,allocation of resources can happen in terms of CCEs which can beequivalent to 36 REs. One CCE can be the minimum PDCCH allocation unit.

As the sTTI length can become smaller, control overhead can increase,which in turn can increase complexity and hence processing delay, andcan could negatively impact latency reduction offered by a low-latencyoperation. To reduce the control signal overhead, scheduling multiplesTTIs via a single grant can be performed, such as sent via an sPDCCH or(E)PDCCH command, which can be referred to as multi-sTTI scheduling. Inanother embodiment to reduce the control signal overhead, sending thecontrol information in a hierarchical manner can be performed, such asmore than one step. For instance, a first step can provide a subset ofcontrol information common to a set of sTTIs at a first time instant,and a second step can provide complementary control informationpertinent to each sTTI at a second time instant. Yet another approachcan include sending the control information in each scheduled sTTI, butwith some DCI bit field reduction compared to the DCIs used for legacy 1ms-TTI. For instance, for a 2/3-symbol sTTI, the Resource Block Group(RBG) size, which for sTTI can be referred to as shortened RBG (sRBG),can be larger, for example 2-6 times, than that used by legacy 1 ms-TTI.

FIG. 2 illustrates example agreed DL sTTI patterns 200. According topossible 3GPP agreements, for 2-symbol DL TTI, the sTTI patterns 200show OFDM symbols per subframe that can be supported for a 2/3 OFDMsymbol-sTTI configuration. For a Control Channel (CC) configured with a2-symbol sTTI operation, for a cross-carrier scheduled CC, the startingsymbol index of the first potential shortened PDSCH (sPDSCH) can beconfigured by Radio Resource Control (RRC). For a self-carrier scheduledCC, the starting symbol index of the first potential sPDSCH can be equalto Control Format Indicator (CFI) value indicated by PCFICH.

The UE 110 can determine the sTTI pattern in accordance with Table 1.

TABLE 1 The starting symbol index of the first potential sPDSCH2-symbols DL sTTI pattern 1, 3 1 2 2

FIG. 3 illustrates an example sTTI DL pattern 300. FIG. 4 illustratesanother example sTTI DL pattern 400. A CRS, as shown in Table 1, can befor each of the two example sTTI DL patterns 300 and 400, illustrated inFIGS. 3 and 4, respectively. The DL sTTI patterns illustrated assume twoport CRS, shown as CRS symbols being shown in FIGS. 3 and 4 as CRSsymbols 301-304 and 401-404, respectively. sPDCCH design principles thathave been adopted by 3GPP include both CRS-based and DMRS-based sPDCCHcan be supported. Radio Access Network layer 1 (RAN1) will not pursueCode Division Multiplexing in Frequency direction (CDM-F) based DMRSpattern for sPDCCH. Legacy PDCCH can be used to transmit shortended DCI(sDCI), such as DCI for sPDSCH and/or shortened PUSCH (sPUSCH).Quadrature Phase Shift Keying (QPSK) can be used for sPDCCH. Tail bitingconvolutional coding can be used for sPDCCH. For CRS-based sPDCCH, intime domain sPDCCH can be transmitted from the first OFDM symbol withinan sTTI and sPDCCH without mapped to the PDCCH region, and frequencyresource for sPDCCH can be informed by the network entity 120.

Different sPDCCH principles can be used. One or two RB set(s) can beconfigured by the higher layer message(s) 140 within the higher layersignaling for sPDCCH frequency resource of the UE 110, with any numberof RBs per set being possibly used. A shortened Resource Element Group(sREG) can consists of 1 RB within 1 OFDM symbol including REs for CRSand/or DMRS applied to DMRS based sPDCCH. An sREG can consist of 1 RBwithin 1 OFDM symbol including REs for CRS and/or DMRS applied to DMRSbased sPDCCH. For sTTI, an sREG can equal 1 RB over 1 OFDM symbolincluding REs for CRS and/or DMRS applied to CRS based sPDCCH. A CRSbased sPDCCH RB set can be configured to the UE 110 by higher-layersignaling either with distributed or localized mapping of a shortenedCCE (sCCE) to sREG. The UE 110 can be configured to monitor sPDCCH RBset(s), such as at most two sPDCCH RB set(s) containing the sTTI UserSecurity Setting (USS) in an sTTI, where one sPDCCH candidate can becontained within one RB set. The UE 110 can be configured to monitor atmost two sPDCCH RB set(s) containing the sTTI User Security Setting(USS) in an sTTI, where one sPDCCH candidate can be contained within oneRB set. The number of OFDM symbols per RB set can be for CRS basedsPDCCH, for 2/3-symbol sTTI, such as 1 or 2 that can be configured byhigher layer. The number of OFDM symbols per RB set for CRS-based sPDCCHcan be 1, 2, and possible 3 symbols for 1-slot sTTI and can beconfigured by higher layer. The number of OFDM symbols per RB set can befor DMRS based sPDCCH, for 2/3-symbol sTTI, such as 2 for 2-symbolsTTI#1,2,3,4, 3 for 3-symbol sTTI#1 and #5, sTTI#0, and/or for 1-slotsTTI: 2, and for 1-slot sTTI: 2. Space-Frequency Block Coding (SFBC) canbe supported for CRS-based sPDCCH, with any number of antenna portsbeing possibly used. Single port DMRS-based sPDCCH demodulation can besupported, with any size bundling size being possibly used. In anexample, two port DMRS-based sPDCCH demodulation can be used, includingbundling size.

A sPDCCH RB set can be configured with at least a set of RBs, where anEPDCCH PRB allocation can be reused, transmission scheme, such asCRS-based or DMRS-based can be used, localized or distributed sCCE tosREG mapping can be used, such as at least for CRS, and, if supportedDMRS-based sPDCCH can be used, with localized or distributed sPDCCHcandidate to sCCE mapping being possible, a number of sPDCCHcandidates/aggregation levels of the RB set can be used, where same ordifferent sPDCCH candidates for different sTTI indexes being possible, anumber of symbols for sPDCCH duration at least in case of CRS-basedtransmission can be used, a Reference Signal (RS) scrambling sequencecan be used, such as Virtual Cell Identities (VCID) in case ofDMRS-based transmission, and other information if needed.

The sPRG size for 2/3os sPDSCH can be N, such as sPRG of N RBs, where Ncan be the same for all system BW or can be system BW specific and N canbe down-selected from [2, 3, 4 and 6]. For up to 2 layers sPDSCH in onesTTI, each layer can map to one different DL DMRS port, and each DMRSport can have Orthogonal Cover Code (OCC)-2 in time domain to supportcode division multiplexing. The DL DMRS pattern can be fixed for 2-layer2/3-symbol sPDSCH, with down-selection can be used between 3 options:option 1: X=3, N=1, option 2: X=2, N=1, and option 3: N>1, X=2N+1 orX=2N. N can be the number of RBs and X can be subcarriers per N RB(s).DL DMRS can be shared among 2 consecutive sTTIs for the same UE 110 for2/3-symbol sPDSCH, without sharing across subframes being supported,sharing across slots can be used, and 3 consecutive sTTIs can be used.DL DMRS RE shift in frequency domain can be supported when collidingwith CRS RE.

The number of required RBs for sPDCCH assuming an example sCCE size of36, and different sPDCCH AL and symbol length that can exist is shown inTable 2 further illustrates 2. Table 2 further illustrates a number ofrequired RBs for sPDCCH for different ALs and number of sPDCCH symbolsassuming an example 36 REs for sCCE that can exist, such as when sCCEcan be similar to CCE used for sTTI operation.

TABLE 2 # of sPDCCH CRS present in one symbols of sPDCCH symbol(s) CCEsize in REs AL # RBs 1 no 36 1 3 1 no 36 2 6 1 no 36 3 9 1 no 36 4 12 1no 36 6 18 1 no 36 8 24 2 no 36 2 3 2 no 36 4 6 2 no 36 6 9 2 no 36 8 12

Similarly, for an example CCE size of 48, shown in Table 3 illustratesthe required number of RB that can exist. Table 3 illustrates a numberof RBs that can be taken for sPDCCH for different ALs and number ofsPDCCH symbols assuming an example forty-eight (48) REs for sCCE.

TABLE 3 # of sPDCCH CRS present in one symbols of sPDCCH symbol(s) CCEsize in REs AL # RBs 1 no 48 1 4 1 no 48 2 8 1 no 48 3 12 1 no 48 4 16 1no 48 6 24 1 no 48 8 32 2 no 48 2 4 2 no 48 4 8 2 no 48 6 12 2 no 48 816

For control channel design for LTE sPDCCH, the embodiments providesolutions for determining by the UE 110 the number of sREGs per sCCE bythe UE 110, the time-frequency position of the sREGs within the time andfrequency resources available for control reception, and the controlcarrying time-frequency resources within sREGs of the control.

Due to varying number of overhead, such as due to presence of CRS in ansTTI and/or DMRS, in control resources, having a fixed number of sREGsper sCCE could lead to a variable number of REs available for controltransmission. In a possible embodiment, the number of sREGs per sCCE canbe fixed, such as 3 sREGs or 4 sREGs. Imposing certain schedulingrestrictions can make it possible to have the number of REs availablefor control transmission be larger than a certain threshold. Examples ofthese restrictions can include not allowing DMRS-based sPDCCH in sTTIsincluding CRS, or sTTIs wherein the control symbols overlap with a CRScontaining symbol. In a possible embodiment, the UE 110 can be excludedfrom performing, such as shall not or based on a configuration sent bynetwork entity 120, monitor DMRS-based sPDCCH when four antenna port CRSis applied. In a possible embodiment, the UE 110 can be excluded frommonitoring DMRS-based sPDCCH in sTTI 3, such as in an sTTI where twocontrol symbols overlap with two CRS containing symbols, when fourantenna port CRS is applied. The network 130 can configure the UE 110 onwhether DMRS-based sPDCCH is possible to occur in sTTIs including CRS orsTTIs wherein the control symbols for DMRS-based sPDCCH overlap with aCRS containing symbol, and accordingly, the UE 110 can monitorDMRS-based sPDCCH in those sTTIs if it is configured to do so.

The DMRS-based sPDCCH can happen in sTTI “n” including CRS, or sTTIswherein the control symbols overlap for DMRS-based sPDCCH with a CRScontaining symbol, only when the DMRS is shared between sTTI “n−1” andsTTI “n” and present in sTTI “n−1”. In an example, the UE 110 can assumeno DMRS is transmitted for sPDCCH candidates in sTTI n and can use theDMRS REs from sTTI n−1 for demodulation of sPDCCH candidates in sTTI nsPDCCH candidate RE mapping in sTTI n can be such that there is norate-matching around DMRS REs. In an example, the UE 110 can use thesame subcarriers for DMRS in sTTI n−1 for attempting to decode sPDCCH insTTI n as would be the case if DMRS was transmitted on sTTI n. In apossible embodiment, the UE 110 can be excluded from monitoringDMRS-based sPDCCH in sTTI 3, such as in an sTTI where two controlsymbols overlap with two CRS containing symbols, when four antenna portCRS can be applied. In a possible example, the UE 110 can assume no DMRSis transmitted for sPDCCH candidates in sTTI n and can use the DMRS REsfrom sTTI n−1 for demodulation of sPDCCH candidates in sTTI n. In anexample, the UE 110 can use the DMRS from sTTI n−1 that at least overlapin frequency with the sREGs associated with the sPDCCH in sTTI n. Incase of PRB bundling, DMRS REs in the bundled PRBs in sTTI n−1 that haveat least one PRB of the bundled PRB overlapping in frequency with thesREGs associated with the sPDCCH in sTTI n can be used for demodulatingand decoding the sPDCCH in sTTI n. If the UE 110 is configured tomonitor DMRS-based sPDCCH, the UE 110 can monitor the DMRS-based sPDCCHin an sTTI containing CRS, or sTTIs wherein the control symbols overlapwith a CRS containing symbol, assuming DMRS is shared between theprevious sTTI and the current sTTI. In such a case, the AggregationLevel (AL) or location of the control can be different between the sTTIssharing the DMRS, but the control resources of the second sTTI can fullyoverlap with control and data resources of the first sTTI containing theDMRS.

In an embodiment, the UE 110 can determine the number of sREGs per sCCEbased on some parameters, or their combinations. For example, for sRBGsize CRS based sPDCCH, for at least localized sREG to sCCE mapping, canbe configured with 1 OFDM symbol length. From a multiplexingperspective, multiplexing data and control or multiplexing two control,an integer number of sCCEs can fit in an sRBG.

FIGS. 5-7 are example illustrations 500, 600, and 700 showing examplesRBGs according to a possible embodiment. For instance, as shown in theillustration 700, two sCCEs each with 3 sREGs can fit in an sRBG size of6 RBs 710, 712, 714, 716, 718, 720, and 722, whereas as illustrated insRBG of the illustration 500, only 1 sCCE with 4 sREGs 510, 512, 514,and 516 can completely fit in the sRBG. With 4 REGs per sCCE asillustrated in illustrations 500 and 600, to multiplex an UL grant with1 sCCE, and a DL assignment with 1 sCCE, 2 sRBGs can be needed, andreusing the unused resources in the second sRBG for DL data transmissioncan become complex if not impossible. In the example shown inillustrations 500 and 600, to at least better use the resources in thesecond symbol of 1^(st) RBG for DL data transmission, such as thoseassigned by sCCEs 610, 612, 614, and 616, the network entity 120 canconfigure the UE 110 associated with sCCE 510, 512, 514, and 516 torate-match around the DMRS in the first symbol. In other words, thenetwork entity 120 can send DMRS for another UE in RBs 510, 512, 514,and 516 in the illustration 500. In another embodiment, the networkentity 120 can transmit DMRS for DL data for the same UE 110, such as ifsCCE 510, 512, 514, and 516 was a DL assignment in in the 1^(st) sRBG,although the DL assignment can be a CRS-based sPDCCH. In that case, ifconfigured, the UE 110 can rate match around the DMRS in the firstsymbol to decode the control. In illustrations 500 and 600, a sCCE cancontain 4 sREGs 510, 512, 514, and 516 in the first sRBG and 4 sREGs610, 612, 614, and 616 in the 2^(nd) sRBG, in an sRBG of 6 RBs, whereasin FIG. 7, 2 CCEs, one illustrated in RBs 710, 712, and 714 and a secondillustrated in RBs 718, 720, an 722, each can be composed of 3 sREGs.Each sREG can be composed of 1 RB. Assuming sCCE, such as RBs 510, 512,514, and 516 are for UL grant and RBs 610, 612, 614, and 616 are for DLassignment, reusing the RBs in the 1^(st) symbol of the 1^(st) sRBG forDL data transmission in FIGS. 5 and 6 can be difficult.

In an example embodiment, for 2-symbol CRS-based sPDCCH with DMRS-basedsPDSCH, using 4 sREGs per sCCE can ease design. However, it can lead tosignificant control overhead, especially for larger ALs. To overcomesuch a deficiency, for AL=1, or odd ALs 4 sREGs can be used. For othereven ALs, 3 sREGs/sCCE can be used, but can have even number of sCCEswithin a sRBG. In an example embodiment, a hybrid scheme of elements ofsolutions as to those previously discussed can be possible, wherein thenumber of sREGs per sCCE can be selected from a limited set but certainscheduling restrictions similar to those explained can ensure the numberof available REs for control can be above a required minimum.

FIG. 8 illustrates an example illustration 800 of 1-symbol lengthCRS-based sPDCCH. Network entity 120 can configure the UE 110 torate-match around the data DMRS present in the control resources whenmonitoring the control candidates. In a 1-symbol CRS-based sPDCCH, theUE 110 can determine control resources in sREGs in the 1^(st) RBs801-803 of the 1^(st) symbol by assuming rate matching around DL dataDMRS REs. Data RBs are illustrated in remaining blocks 804-812 ofCRS-based sPDCCH 800, with “D” representing DL data DMRS. The DMRSs aresymbolically illustrated and the DMRSs may or may not occupy the centerresources of a given RB.

In another embodiment, the UE 110 can determine whether to rate-matcharound DMRS for control monitoring based on at least whether DMRS-basedsPDSCH is configured. For example, this can be useful for 1-symbolCRS-based sPDCCH with both localized and distributed sREG to sCCEmappings. If DMRS was shared between two consecutive sTTIs, such as sTTI“n−1” and sTTI “n”, the UE 100 can assume DMRS positions are puncturedin the control region in sTTI “n”, assuming DMRS presence in sTTI “n−1”,since the UE 110 does not know before decoding the sPDCCH in sTTI “n” ifthe DMRS was shared across sTTI “n−1”, and “n”. In a possibleembodiment, the UE 110 can know from sTTI “n−1” that the UE 110 candecode sPDCCH assuming no DMRS is present in sTTI n for DMRS basedsPDCCH. In another embodiment, if the UE 110 is configured to rate-matcharound DMRS for sPDCCH, such as CRS-based sPDCCH, the UE 110 canrate-match around the DMRS. The UE 110 can assume a non-UE specificprecoder can be used/associated with the DMRS in control resources insTTI n−1. sPDCCH in sTTI “n” can use the DMRS REs from sTTI “n−1” on theRBs corresponding to the sPDCCH. The Antenna Port (AP) for the sPDCCHcan be based on the candidate that can be monitored in sTTI “n”. In3-symbol sTTI, the last two symbols of the sTTI can have DL data DMRS,and the control containing symbol, such as the 1^(st) symbol of thesTTI, can be decoded assuming no DMRS present. If DMRS-based sPDSCH isused in the next two symbols of the 3-symbol sTTI, DMRS distributionpattern in the next two symbols can be determined based on the locationof the sREGs in the first symbol.

FIG. 9 illustrates an example 3-symbol sTTI 900, such as sTTI 5 in FIG.2. The DMRS pattern for sPDSCH can be determined based on the locationof the sREGs in the 1^(st) symbol, as show in the first four RBs 901-904of the 1^(st) symbol, with the remaining RBs 905-918 not including REGs.The 3-symbol sTTI 900 includes a bundling size=3 RBs, and X=2N+1, with 7DMRS per 3 RBs.

If bundling size or DMRS distribution pattern can be different forsPDSCH and DMRS-based sPDCCH, they can share DMRS within an sRBG. In apossible embodiment, an sPDSCH bundling pattern can take precedence. Inanother embodiment, both sPDCCH and sPDSCH bundling patterns can bealigned. For 3GPP agreements, in a possible embodiment a single portDMRS-based sPDCCH demodulation can be supported. In another embodiment,two port DMRS-based sPDCCH demodulation can be supported.

FIG. 10 is an example illustration 1000 showing a DMRS sharing examplebetween DMRS-based sPDCCH and sPDSCH. FIG. 11 is an example illustration1100 showing another DMRS sharing example between DMRS-based sPDCCH andsPDSCH. For example, 3sREGs can be used per sCCE in a 2-symbol sTTI,such as with 2-symbol sPDCCH, such as shown in the sREGs 1001 and 1002of the 1^(st) symbol and the sREG 1007 of the 2^(nd) symbol in theillustration 1000, or 4sREGs can be used per sCCE in a 3-symbol sTTIwith 3-symbol sPDCCH, such as shown in the first two sREGs 1101 and 1102of the 1^(st) symbol, the 1^(st) sREG 1107 of the 2^(nd) symbol, and the1st sREG 1113 of the 3^(rd) symbol, of the 1^(st) sRBG 1020 shown inFIG. 11. The data part including sREGs 1103-1106, 1108-1112, and1114-1118 of the 3-symbol sTTI in the illustration 1100 or the data partincluding sREGs 1003-1006 and 1008-1012 of the 2-symbol sTTI in theillustration 1000 can contain DMRS resources in an RB not belonging tothe control part including sREGs 1101, 1102, 1107, and 1113 of the3-symbol sTTI in the illustration 1100 or the control part includingsREGs 1001, 1002, and 1007 of the 2-symbol sTTI in the illustration1000, respectively. The UE 110 can determine the DMRS pattern within theRB(s) where DMRS can be shared between the data and control, such as insREGs 1008 in the illustration 1000 and 1102 in the illustration 1100,such as based on the DMRS pattern for data, based on the DMRS patternfor control, and/or based on both.

FIG. 12 illustrates an example sCCE structure 1200 for DMRS-based sPDCCHwith 3 sREGs per sCCE. The RBs, such as the control RBs, that constitutean RB bundle can be different for different CCE indexes. For example,sCCE 0 can use the 1^(st) AP and sCCE 1 can use the 2^(nd) AP. AP can bebased on Radio Network Temporary Identifier (RNTI) for the UE 110 and/orthe sCCE index, such as lowest sCCE index forming the sPDCCH candidate.For example, assuming 3 sREGs, each composed of 1 RB, per sCCE, theexample sCCE structure 1200 can be possible in a 2-symbol sTTI for aDMRS-based sPDCCH. The illustrated “D” can represent a DMRS. The RBs insREGs corresponding to the 1st sCCE and the 2nd sCCE are shown in RBs1202, 1204, and 1206, and 1208, 1210, and 1212, respectively. The firstand second RB bundles are shown by rectangle 1214, and rectangle 1216,respectively. The RB bundling example shown in FIG. 12 can be for AL=1candidates, such as when control contains only 1 sCCE. In anotherembodiment, higher ALs, such as AL=2, can have a different RB bundlingsize than that shown in FIG. 12.

FIG. 13 illustrates another example sCCE structure 1300. In a possibleembodiment, the example sCCE structure 1300 can be for a DMRS-basedsPDCCH with 3 sREGs per sCCE such as 1301, and higher ALs, such as AL=2,can have a different RB bundling size and can be composed of two sCCEs.“D” represents DMRS. The RB bundle size in frequency can be 3.

The UE 110 can determine the location of the 1-symbol sPDCCH within ansTTI of 2/3 symbol, or a 2-symbol sPDCCH within 3-symbol sTTI based onone or more of the length of the configured sPDCCH, sTTI index, and theoverhead, such as reference symbol overhead. Such an approach can behelpful in avoiding the CRS overhead to reduce the number of availableREs in an RB used for control resources, such as in an sREG. Forexample, an sPDCCH with 2-symbol length can start from the first symbolin sTTI 1, such as in DL sTTI pattern 2 300 and 400 shown in FIGS. 3 and4, while for sTTI 5, a 2-symbol sPDCCH can start from the 2^(nd) symbolof the sTTI.

PBCH in LTE can carry essential information referred to as a MasterInformation Block (MIB). PBCH can transmitted over 6 RBs (72subcarriers) centered around a Direct Current (DC) subcarrier in thefirst 4 OFDM symbols of the 2^(nd) of sub frame 0 of a radio frame, eachradio frame for LTE can be 10 ms and each slot is 5 ms. The DCsubcarrier can be the subcarrier whose frequency can be equal to the RFcenter frequency of the transmitting station.

In a possible embodiment, for sTTI operation, RBs containing PBCH arenot included in the mapping of control resources in sTTI 3 and sTTI 4.The mapping of control resources can be “sREGs to sCCE mapping” and/or“sCCE to sPDCCH aggregation mapping”. FIG. 14 illustrates example sRBGs1400 where two sRBGs 1410 and 1420 can overlap with PBCH resources 1430.The UE 110 can determine the mapping of control resources based on thepresence of the PBCH. FIG. 15 illustrates example sTTI 3 and sTTI 4 1510in a subframe that can overlap with PBCH. The mapping of controlresources can be different than the mappings used in the sTTIs notoverlapping with PBCH. For example, if CRS-based/DMRS sPDCCH with AL=4can be used in sTTI 4 over two symbols, assuming 36 REs/sCCE, instead ofhaving a sPDCCH decoding candidate spanning the left entire example sRBGillustrated in FIG. 15, which for example can be the case for some othersTTIs in the subframe/or other subframes, the candidate can span theentire resources, excluding the PBCH RBs of both right and left sRBGs.

In another example illustrated in FIG. 15, an example distributedCRS-based/DMRS-based sPDCCH candidate 1520 can take RBs in the central 6RBs in sTTIs 3 or sTTI 4 in a subframe not containing PBCH or in othersTTIs if a subframe containing PBCH, can take a different set of RBsoutside the PBCH RBs in an sTTI overlapping with PBCH. The PBCH can spanacross 1^(st) and 2^(nd) sRBGs. FIG. 15 illustrates an example ofdifferent control resource mapping, with AL=2 and with 4 sREG/sCCE, foran sTTI overlapping with PBCH 1510 in an example sTTI 3, and sTTI 4 intime and for another sTTI not overlapping with PBCH candidate 1510. Inan example, the PBCH candidate 1510 can span across 1^(st) and 2^(nd)sRBGs 1512 and 1514 and the sPDCCH candidate 1520 can span across 1^(st)and 2^(nd) sRBGs 1522 and 1524, as illustrated.

FIG. 16 illustrates a similar example to the example shown in FIG. 15but with a single sRBG of twelve (12) RBs. In contrast to the exampleshown in FIG. 15, a distributed CRS-based/DMRS-based sPDCCH candidate1620 can span a width of a single sRBG. Similarly, in a possibleembodiment, for sTTI operation, RBs containing Secondary SynchronizationSignal (SSS)/Primary Synchronization Signal (PSS) can be excluded frommapping of control resources in sTTIs overlapping with SSS/PSS in thetime domain. The mapping of control resources can be “sREGs to sCCEmapping” and/or “sCCE to sPDCCH aggregation mapping.”

In another embodiment, in a case where sRBG can be larger than 6 RBs,the sRBG containing/overlapping with PBCH can be excluded frommapping/monitoring control information, such as when sPDCCH PRB-set canbe excluded from overlap with PBCH containing sRBG, in example, sTTIs 3& 4, having a different sREG to sCCE mapping, having a different numberof sREGs per sCCE in such sRBG, having a different monitoring rule inthat case, or having a different sRBG definition in those sTTIs. Theseprinciples can be applied similarly for primary or secondarysynchronization signals. The UE 110 can be excluded from being expectedto monitor an EPDCCH candidate, if an ECCE corresponding to that EPDCCHcandidate can be mapped to a PRB pair that can overlap in frequency witha transmission of either PBCH or primary or secondary synchronizationsignals in the same subframe.

The minimum unit of resource allocation for a resource allocation typefor sTTI operation, referred to as sRBG, size can be set such thatmultiple system, or sTTI-related, Bandwidth (BW) can have the same sRBGsize. An sRBG can be an integer of RBG size which can be a function ofsystem BW. For instance, for 50 RB system BW, the RBG size is 3 RB, andfor 75 and 100 RB system BW, the RBG size is 4 RBs. An sRBG for 50 RB BWcan compose of 4 RBGs resulting in 12 REs and an sRBG for 75 or 100 RBBW, can compose of 3 RBGs resulting in 12 REs.

In another embodiment, a fixed number of sREGs per sCCE can be used fora common design perspective across sTTIs. For example, an sREG caninclude 1 RB within 1 OFDM symbol. A legacy/regular REG can include 4REs. A legacy/regular RB can be a unit of 84 REs, such as 21 REGs, whichis 12 subcarriers by 7 symbols. Using Extended Cyclic Prefix, the numberof symbols within a subframe can become 6 and a single RB can be a unitof 72 REs, such as 18 REGs. 4 sREGs per sCCE can be considered as aconservative approach. Alternatively, 3 sREGs per sCCE can beconsidered, however in cases of high overhead, higher aggregation levelsmight be needed or AL=1 candidates may be restricted to certainlocations. Considering resource allocation bit reduction for sTTIcompared to 1 ms DCIs, the sPDCCH payload can be smaller than that ofthe PDCCH and less REs/CCE can be used. In another embodiment, sREGsforming an sCCE can be mapped to the RBs of an RB set under thelocalized sREG-to-sCCE mapping on continuous RBs belonging to an sRBG,such as when sCCEs don't cross the sRBG boundary, with time firstmapping.

In another embodiment, regarding how the decoding candidates peraggregation level get mapped to the available resources if the number ofsymbols per RB set can be more than 1, the decoding candidates, such asPDCCH decoding candidates, per aggregation level can be mapped to theavailable resources using frequency first mapping in which small ALs aremapped within the first symbol and higher ALs are distributed amongstsymbols. This methodology can be used when higher ALs may not be able tofit within the sPDCCH resources given in a single symbol. This can alsocan be used when the UE 110 needs higher AL that are not generally ingood channel condition and they do not generally attain much benefit inlatency reduction even with a single HARQ timeline. The decodingcandidates can be the number of CCE indexes searched by the UE 110 in asubframe for a particular search space.

The decoding candidates per aggregation level can be mapped to theavailable resources based on the RB-set size, such as smaller than agiven number “K” of RB in the RB set, over two symbols. Otherwise thedecoding candidates can be mapped over a single symbol, which one of thetwo possible symbols for a single symbol mapping can be Radio ResourceControl (RRC) or based on the UE ID and subframe/slot/sTTI index. Inanother embodiment, generally, DMRS-based sPDCCH can be used to attainbeamforming gain in which case it can use local sREG-to-sCCE mapping,but in Multicast-Broadcast Single-Frequency Network (MBSFN) subframes orin normal subframes but in sTTIs without CRS, DMRS-based sPDCCH can beused to attain frequency diversity. The UE 110 in those sTTIs/subframescan assume DMRS-based sPDCCH with localized mapping, if it is configuredby the network 130.

In another embodiment, in regarding how many symbols can be consideredper RB set for DMRS-based sPDCCH over the 3-symbol sTTIs, fromcommonality perspective with two-symbol sTTI, two symbols can be usedper RB set for DMRS-based sPDCCH over the 3-symbol sTTIs. This can alsoavoid CRS containing symbol overlapping with control resources in sTTI1& 5.

According to different scenarios, DMRS for orphan symbols in a 3-symbolsTTI can be assigned a different AP, the same AP for the same UE forsPDSCH, or it can be used for CRS-based sPDSCH. The network 130 canimplicitly or explicitly configure one or more of these three scenariosbased on the configuration or specification, and the UE 110 can assumeone or more of those scenarios. In another embodiment, some ComponentCarriers (CCs) in a case of carrier aggregation can use CRS-based sPDCCHand some CC's can use DMRS-based sPDCCH for scheduling, such as per CCconfiguration. Cross-carrier scheduling of one CC from another CC canallow DMRS-based sPDCCH scheduling CRS-based sPDSCH. In anotherembodiment, a fallback mode can be utilized. The UE 110 can beconfigured to monitor DMRS-based sPDCCH, but in some subframes it canmonitor CRS-based sPDCCH as a fallback if one or more of fallbackcondition occur.

FIG. 17 illustrates an example flowchart 1700 illustrating operation ofan apparatus such as the UE 110, according to a possible embodiment. At1710, the higher layer message(s) 140 from the network entity 120, suchas a base station, indicating to monitor a control channel using DMRS'sin an sTTI in a subframe can be received, where the higher layer can behigher than a physical layer, and where the sTTI can be shorter than asubframe-length TTI.

At 1720, a first control channel candidate in the sTTI can be attemptedto be decoded, for example by the UE 110. The first control channelcandidate can comprise a first sCCE (sCCE1) spanning a first set ofsREGs in a frequency domain using a first DMRS on a first AP. A firstprecoder can apply to all DMRS REs in the first set of sREGs, where asCCE corresponds to the sTTI. For sTTI, 1 sREG can equal 1 RB over onesymbol. For example, referring to FIG. 12, a first set of sREGs (sCCE1)can occupy REs in RB1, sym 0 and a second set of sREGs (sCCE2) canoccupy REs in RB1, sym 1.

At 1730, a second control channel candidate in the sTTI can be attemptedto be decoded, for example by the UE 110. The second control channelcandidate can comprise a second sCCE spanning a second set of sREGs inthe frequency domain using a second DMRS on a second AP. A secondprecoder can apply to all DMRS REs in the second set of sREGs. A firstsREG of the first set of sREGs can occupy a first set of REs in a givenRB in a first OFDM symbol of the sTTI and a second sREG of the secondset of sREGs (sCCE2) can occupy a second set of REs, in the given RB ina second OFDM symbol of the sTTI, where the first OFDM symbol can bedifferent from the second OFDM symbol.

According to a possible embodiment, some sREGs in the first set of sREGs(sCCE1) occupy same RBs in both the first OFDM symbol and the secondOFDM symbol and another sREG in the first set of sREGs (sCCE1) for thegiven RB occupying only one OFDM symbol. For example, referring to FIG.12, a first set of sREGs (sCCE1) can occupy REs in RB1, sym 0 and asecond set of sREGs (sCCE2) can occupy REs in RB1, sym 1. According to apossible embodiment, the control candidates can include one or moreCCEs. According to a possible embodiment, the number of PRBs in a sCCEcan be the same for each sCCE. According to a possible embodiment, acontrol channel can be a sPDCCH and the flowcharts can be performed bythe UE 110.

According to a possible embodiment, a precoding granularity of aprecoder for the first sCCE can comprise multiple resource blocks in thefrequency domain that are equal to the number resource blocks in thefirst OFDM symbol. The precoding granularity can be based on PrecoderResource block Group (PRG) bundling. As understood to one of ordinaryskill in the art, precoder granularity of a number of PRBs can mean thesame precoder can be provided for the number of PRBs.

According to a possible embodiment, the first control channel candidateand the second control channel candidate can each comprise a singlesCCE. For example, this can be for an aggregation level 1. A number ofsCCEs in a control channel candidate can also be based on the sCCEaggregation level. A sCCE can include 3 sREGs, such as 3 RBs. Accordingto a possible embodiment, the first AP can be used for even controlchannel (sPDCCH) candidates of a size of one sCCE and the second AP canbe used for odd control channel (sPDCCH) candidates of a size of oneCCE. According to a possible embodiment, the first AP can be furtherbased on a UE Identifier (ID). For example, the UE ID can equate to aUser Equipment Identifier, such as Cell-RNTI (C-RNTI). According to apossible embodiment, the first AP can be further based on an index ofthe first sCCE.

In a possible embodiment, the higher layer message can be a first higherlayer message, the sTTI can be a first sTTI, and the subframe can be afirst subframe, flowchart 1700 can further comprise receiving a downlinksignal from the base station, determining a number of CRS APs based onthe received downlink signal, receiving a second higher layer message tomonitor a third control channel candidate using DMRS's in at least onesTTI in a second subframe, where the second higher layer can be higherthan a physical layer. Flowchart 1700 can further include determiningwhether to monitor the third control channel candidate using DMRS's in asecond sTTI of the at least one sTTI based on the determined number ofCRS APs in response to receiving the second higher layer message andattempting to decode the third control channel candidate using a thirdDMRS in the second sTTI if it can be determined to monitor the controlchannel candidate using DMRS in the second sTTI.

In a possible embodiment, control symbols in the sTTI can overlap with aCRS containing symbol. Flowchart 1700 can further include determining toexclude monitoring of a sPDCCH using given DMRS's in the sTTI of thesTTI when the determined number of CRS APs can be larger than athreshold number of APs.

FIG. 18 illustrates another example flowchart 1800 illustratingoperation of an apparatus such as the UE 110, according to a possibleembodiment. At 1810, a higher layer message from a base station formonitoring control channel candidates in at least one sTTI in a subframeand set of RBs corresponding to control channel candidates in the atleast one sTTI, can be received, where the higher layer can be higherthan a physical layer, and where a sTTI can be shorter than asubframe-length TTI.

At 1820, whether at least one RB of the set of RBs at least partiallyoverlaps with a broadcast control channel or signal can be determined.At 1830, control resource REs used for transmission of a control channelcandidate based on the determining whether at least one RB of the set ofRBs at least partially overlaps in frequency with a broadcast controlchannel or signal, can be determined.

At 1830, decoding the control channel candidate in the at least one sTTIaccording to the determined control resource REs, can be attempted,wherein the control channel candidate can comprise an sCCE spanning aset of sREGs in a frequency domain.

According to a possible embodiment, the flowchart 1800 can furtherinclude using a first mapping to map control information to controlresource REs used for transmission of the control channel candidate ifat least one RB of the set of RBs at least partially overlaps infrequency with a broadcast control channel or signal, and using a secondmapping to map control information to control resource REs used fortransmission of the control channel candidate if none of the RBs of theset of RBs overlap in frequency with a broadcast control channel orsignal, wherein the first and the second mappings are different.

In an example, the control information can be excluded from being mappedto the at least one RB of the set of RBs that at least partiallyoverlaps with the broadcast control channel or signal. In an example,control information can be excluded from being mapped to a second set ofRBs if the at least one RB of the set of RBs that at least partiallyoverlaps with the broadcast control channel or signal belong to thesecond set of RBs, wherein the second set of RBs can be a subset of theset of RBs. In an example, the second set of RBs can form a resourceblock group (RBG), where an RBG can be a unit of scheduling downlinkdata transmissions. In an example, the RBG size can be larger than 6resource blocks.

According to a possible embodiment, the set of sREGs of the sCCE can bea first set of sREGs if at least one RB of the set of RBs at leastpartially overlaps in frequency with a broadcast control channel orsignal. According to a possible embodiment, a second set of sREGs ifnone of the RBs of the set of RBs overlap in frequency with a broadcastcontrol channel or signal. In an example, the first and the second setof sREGs can be different. In an example, the first set of sREGs can bea subset of the second set of sREGs.

According to a possible embodiment, the control channel candidate cancomprise a set of sCCEs, and the set of sCCEs can be a first set ofsCCEs if at least one RB of the set of RBs at least partially overlapsin frequency with a broadcast control channel or signal, and can be asecond set of sCCEs if none of the RBs of the set of RBs overlap infrequency with a broadcast control channel or signal. In an example, thefirst and the second set of sCCEs can be different. According to apossible embodiment, the flowchart 1800 can further include monitoring,such as by UE 110, the control channel using DMRS's in the at leastsTTI. In an example, at least a subset of the set of sREGs can use aDMRS on an AP, where a single-layer precoder applies to all DMRS REs inthe at least subset of the set of sREGs. In a possible embodiment, theat least one sTTI can comprise one of a first two sTTIs in a second slotof a subframe. In a possible embodiment, at least one RB of the set ofRBs can comprise synchronization signals, the REs in the at least one RBof the set of RBs not used for determining control resource elements forthe control channel candidate in the at least one sTTI overlapping withthe synchronization signals in the time domain.

FIG. 19 illustrates an example flowchart 1900 illustrating operation ofan apparatus such as the network entity 120, according to a possibleembodiment. At 1910, a higher layer message indicating to monitor acontrol channel using DMRS's in a sTTI in a subframe can be transmitted.The higher layer can be higher than a physical layer, and the sTTI canbe shorter than a subframe-length TTI.

At 1920, a first control channel candidate in the short transmit timeinterval can be transmitted, for example by the network entity 120. Thefirst control channel candidate can comprise a first sCCE (sCCE1)spanning a first set of sREGs in a frequency domain using a first DMRSon a first AP. A first precoder can apply to all DMRS REs in the firstset of sREGs, where a sCCE corresponds to the sTTI. For sTTI, 1 sREG canequal 1 RB over one symbol. For example, referring to FIG. 12, a firstset of sREGs (sCCE1) can occupy REs in RB1, sym 0 and a second set ofsREGs (sCCE2) can occupy REs in RB1, sym 1.

At 1930, a second control channel candidate in the sTTI can betransmitted, for example by the network entity 120. The second controlchannel candidate can comprise a second sCCE spanning a second set ofsREGs in the frequency domain using a second DMRS on a second AP. Asecond precoder can apply to all DMRS REs in the second set of sREGs. Afirst sREG of the first set of sREGs can occupy a first set of REs in agiven RB in a first OFDM symbol of the sTTI and a second sREG of thesecond set of sREGs (sCCE2) can occupy a second set of REs, in the givenRB in a second OFDM symbol of the sTTI, where the first OFDM symbol canbe different from the second OFDM symbol.

According to a possible embodiment, some sREGs in the first set of sREGs(sCCE1) occupy same RBs in both the first OFDM symbol and the secondOFDM symbol and another sREG in the first set of sREGs (sCCE1) for thegiven RB occupying only one OFDM symbol. For example, referring to FIG.12, a first set of sREGs (sCCE1) can occupy REs in RB1, sym 0 and asecond set of sREGs (sCCE2) can occupy REs in RB1, sym 1. According to apossible embodiment, the control candidates can include one or moreCCEs. According to a possible embodiment, the number of PRBs in a sCCEcan be the same for each sCCE. According to a possible embodiment, acontrol channel can be a sPDCCH and the flowcharts can be performed bythe UE 110.

According to a possible embodiment, a precoding granularity of aprecoder for the first sCCE can comprise multiple resource blocks in thefrequency domain that are equal to the number resource blocks in thefirst OFDM symbol. The precoding granularity can be based on PrecoderResource block Group (PRG) bundling. As understood to one of ordinaryskill in the art, precoder granularity of a number of PRBs can mean thesame precoder can be provided for the number of PRBs.

According to a possible embodiment, the first control channel candidateand the second control channel candidate can each comprise a singlesCCE. For example, this can be for an aggregation level 1. A number ofsCCEs in a control channel candidate can also be based on the sCCEaggregation level. A sCCE can include 3 sREGs, such as 3 RBs. Accordingto a possible embodiment, the first AP can be used for even controlchannel (sPDCCH) candidates of a size of one sCCE and the second AP canbe used for odd control channel (sPDCCH) candidates of a size of oneCCE. According to a possible embodiment, the first AP can be furtherbased on a UE Identifier (ID). For example, the UE ID can equate to aUser Equipment Identifier, such as Cell-RNTI (C-RNTI). According to apossible embodiment, the first AP can be further based on an index ofthe first sCCE.

FIG. 20 illustrates an example flowchart 2000 illustrating operation ofan apparatus such as the network entity 120, according to a possibleembodiment. At 2010, a higher layer message for monitoring controlchannel candidates in at least one sTTI in a subframe and set of RBscorresponding to control channel candidates in the at least one Stti canbe transmitted. The higher layer can be higher than a physical layer. AnsTTI can be shorter than a subframe-length TTI. At least one RB of theset of RBs at least can partially overlap with a broadcast controlchannel or signal.

At 2020, whether at least one RB of the set of RBs at least partiallyoverlaps with a broadcast control channel or signal can be determined.

At 2030, control REs used for transmission of a control channelcandidate based on the determining whether at least one RB of the set ofRBs at least partially overlaps in frequency with a broadcast controlchannel or signal can be determined.

At 2040, the control channel candidate in the at least one sTTIaccording to the determined control REs can be transmitted, wherein thecontrol channel candidate comprises an sCCE spanning a set of sREGs in afrequency domain.

According to a possible embodiment, the flowchart 2000 can furtherinclude using a first mapping to map control information to controlresource REs used for transmission of the control channel candidate ifat least one RB of the set of RBs at least partially overlaps infrequency with a broadcast control channel or signal, and using a secondmapping to map control information to control resource REs used fortransmission of the control channel candidate if none of the RBs of theset of RBs overlap in frequency with a broadcast control channel orsignal, wherein the first and the second mappings are different.

In an example, the control information can be excluded from being mappedto the at least one RB of the set of RBs that at least partiallyoverlaps with the broadcast control channel or signal. In an example,control information can be excluded from being mapped to a second set ofRBs if the at least one RB of the set of RBs that at least partiallyoverlaps with the broadcast control channel or signal belong to thesecond set of RBs, wherein the second set of RBs can be a subset of theset of RBs. In an example, the second set of RBs can form a resourceblock group (RBG), where an RBG can be a unit of scheduling downlinkdata transmissions. In an example, the RBG size can be larger than 6resource blocks.

According to a possible embodiment, the set of sREGs of the sCCE can bea first set of sREGs if at least one RB of the set of RBs at leastpartially overlaps in frequency with a broadcast control channel orsignal. According to a possible embodiment, a second set of sREGs ifnone of the RBs of the set of RBs overlap in frequency with a broadcastcontrol channel or signal. In an example, the first and the second setof sREGs can be different. In an example, the first set of sREGs can bea subset of the second set of sREGs.

According to a possible embodiment, the control channel candidate cancomprise a set of sCCEs, and the set of sCCEs can be a first set ofsCCEs if at least one RB of the set of RBs at least partially overlapsin frequency with a broadcast control channel or signal, and can be asecond set of sCCEs if none of the RBs of the set of RBs overlap infrequency with a broadcast control channel or signal. In an example, thefirst and the second set of sCCEs can be different. In a possibleembodiment, the at least one sTTI can comprise one of a first two sTTIsin a second slot of a subframe. In a possible embodiment, RBs containingsynchronization signals can be excluded from being included in themapping of control resources in sTTIs overlapping with synchronizationsignals in the time domain.

FIG. 21 illustrates an example block diagram of an apparatus 2100, suchas the UE 110, the network entity 120, the network entity 125, any ofthe entities within the network 130, and/or any other wireless ornon-wireless communication device disclosed herein, according to apossible embodiment. The apparatus 2100 can include a housing 2110, acontroller 2120 coupled to the housing 2110, audio input and outputcircuitry 2130 coupled to the controller 2120, a display 2140 coupled tothe controller 2120, a transceiver 2170 coupled to the controller 2120,at least one antenna 2175 coupled to the transceiver 2170, a userinterface 2160 coupled to the controller 2120, a memory 2150 coupled tothe controller 2120, and a network interface 2180 coupled to thecontroller 2120. The apparatus 2100 may not necessarily include all ofthe illustrated elements for different embodiments of the presentdisclosure. The apparatus 2100 can perform the methods described in allthe embodiments.

The display 2140 can be a viewfinder, a Liquid Crystal Display (LCD), aLight Emitting Diode (LED) display, an Organic Light Emitting Diode(OLED) display, a plasma display, a projection display, a touch screen,or any other device that displays information. The transceiver 2170 canbe one or more transceivers that can include a transmitter and/or areceiver. The audio input and output circuitry 2130 can include amicrophone, a speaker, a transducer, or any other audio input and outputcircuitry. The user interface 2160 can include a keypad, a keyboard,buttons, a touch pad, a joystick, a touch screen display, anotheradditional display, or any other device useful for providing aninterface between a user and an electronic device. The network interface2180 can be a Universal Serial Bus (USB) port, an Ethernet port, aninfrared transmitter/receiver, an IEEE 1394 port, a wirelesstransceiver, a WLAN transceiver, or any other interface that can connectan apparatus to a network, device, and/or computer and that can transmitand receive data communication signals. The memory 2150 can include aRandom Access Memory (RAM), a Read Only Memory (ROM), an optical memory,a solid state memory, a flash memory, a removable memory, a hard drive,a cache, or any other memory that can be coupled to an apparatus.

The apparatus 2100 or the controller 2120 may implement any operatingsystem, such as Microsoft Windows®, UNIX®, or LINUX®, Android™, or anyother operating system. Apparatus operation software may be written inany programming language, such as C, C++, Java or Visual Basic, forexample. Apparatus software may also run on an application framework,such as, for example, a Java® framework, a .NET® framework, or any otherapplication framework. The software and/or the operating system may bestored in the memory 2150 or elsewhere on the apparatus 2100. Theapparatus 2100 or the controller 2120 may also use hardware to implementdisclosed operations. For example, the controller 2120 may be anyprogrammable processor. Disclosed embodiments may also be implemented ona general-purpose or a special purpose computer, a programmedmicroprocessor or microprocessor, peripheral integrated circuitelements, an application-specific integrated circuit or other integratedcircuits, hardware/electronic logic circuits, such as a discrete elementcircuit, a programmable logic device, such as a programmable logicarray, field programmable gate-array, or the like. In general, thecontroller 2120 may be any controller or processor device or devicescapable of operating an apparatus and implementing the disclosedembodiments. Some or all of the additional elements of the apparatus2100 can also perform some or all of the operations of the disclosedembodiments.

In operation as the UE 110, the transceiver 2170 can transmit andreceive the various signals described above. In a possible embodiment,for example the transceiver 2170 can receive a higher layer message(s)140, from the network entity 120, such as a base station, indicating tomonitor a control channel using DMRS's in an sTTI in a subframe, wherethe higher layer can be higher than a physical layer, and where the sTTIcan be shorter than a subframe-length TTI. In a possible embodiment, forexample the controller 2120 can attempt to decode a first controlchannel candidate in the sTTI. The first control channel candidate cancomprise a first sCCE spanning a first set of sREGs in a frequencydomain using a first DMRS on a first AP. A first precoder can apply toall DMRS REs in the first set of sREGs, where a sCCE corresponds to ansTTI.

In a possible embodiment, for example the controller 2120 can attempt todecode a second control channel candidate in the sTTI. The secondcontrol channel candidate can comprise a second sCCE spanning a secondset of sREGs in the frequency domain using a second DMRS on a second AP.A second precoder can apply to all DMRS REs in the second set of sREGs,where a first sREG of the first set of sREGs can occupy a first set ofREs in a given RB in a first OFDM symbol and a second sREG of the secondset of sREGs can occupy a second set of REs, in the given RB in a secondOFDM symbol, where the first OFDM symbol can be different from thesecond OFDM symbol.

Furthermore, in addition to the possible embodiments discussed above, afurther possible embodiment can include an apparatus and method that caninclude the transceiver 2170 to receive a downlink signal from a basestation and determining a number of CRS APs based on the receiveddownlink signal. The apparatus and method can further include thetransceiver 2170 to receive a higher layer message for monitoring acontrol channel (sPDCCH) candidate using DMRS's in at least one sTTI ina subframe, where the higher layer can be higher than a physical layer,and where an sTTI can be shorter than a subframe-length TTI anddetermining whether to monitor the control channel candidate using DMRSin a first sTTI of the at least one sTTI based on the determined numberof CRS APs in response to receiving the higher layer message. Theapparatus and method can yet further include the controller 2120 toattempt to decode the control channel candidate using DMRS in the firstsTTI if it can be determined to monitor the control channel candidateusing DMRS in the first sTTI. The apparatus can be the UE 110 and methodcan be performed by the UE 110. In an example, the higher layer can behigher than the physical layer in that the higher layer message can bereceived on a layer above the physical layer. The control symbols in thefirst sTTI can overlap with a CRS containing symbol, and the apparatusand method can even yet further include determining to not monitor thesPDCCH using DMRS in a first sTTI of the one or more sTTIs when thedetermined number of CRS APs can be larger than a threshold number ofAPs. For example, the threshold can be two APs. In a possibleembodiment, the UE 110 shall not monitor DMRS-based sPDCCH in sTTI 3,such as in an sTTI where two control symbols overlap with two CRScontaining symbols, when four AP CRS can be applied.

Another possible embodiment can include an apparatus and method that caninclude the transceiver 2170 that can receive a higher layer messagefrom a base station for monitoring control channel candidates in atleast one sTTI in a subframe and set of RBs corresponding to controlchannel candidates in the at least one sTTI, where the higher layer canbe higher than a physical layer, and where the sTTI can be shorter thana subframe-length TTI. The controller 2120 can determine whether atleast one RB of the set of RBs at least partially overlaps with abroadcast control channel or signal and determine control REs used fortransmission of a control channel candidate based on the determinationwhether the at least one RB of the set of RBs at least partiallyoverlaps with the broadcast control channel or signal. The controller2120 can further attempt to decode the control channel candidate in theat least one sTTI according to the determined control REs, where thecontrol channel candidate comprises a sCCE spanning a set of sREGs in afrequency domain, the set of sREGs comprising the determined controlREs.

In a possible embodiment, if at least one RB of the set of RBs at leastpartially overlaps in frequency with a broadcast control channel orsignal, the controller 2120 can use a first mapping to map controlinformation to control REs used for transmission of the control channelcandidate and if none of the RBs of the set of RBs overlap in frequencywith a broadcast control channel or signal, the controller 2120 canusing a second mapping to map control information to control REs usedfor transmission of the control channel candidate, wherein the first andthe second mappings are different. The control information can beexcluded from being mapped to the at least one RB of the set of RBs thatat least partially overlaps with the broadcast control channel orsignal.

The set of RBs can be a first set of resource blocks, wherein thecontrol information can be excluded from being mapped to a second set ofRBs if the at least one RB of the first set of RBs that can at leastpartially overlap with the broadcast control channel or signal belong tothe second set of RBs, wherein the second set of RBs can be a subset ofthe first set of RBs. The second set of RBs can form a RB group, where aRB group can be a unit of scheduling downlink data transmissions. The RBgroup size can be larger than 6 RBs.

The set of shortened RE groups of the sCCE can be a first set of sREGsif at least one RB of the set of RBs at least partially overlaps infrequency with a broadcast control channel or signal, and a second setof shortened resource element groups if none of the RBs of the set ofRBs overlap in frequency with a broadcast control channel or signal,wherein the first and the second set of sREGs can be different. Thefirst set of sREGs can be a subset of the second set of shortenedresource element groups. The control channel candidate comprises a setof sCCEs, and the set of sCCEs can be a first set of sCCEs if at leastone RB of the set of RBs at least partially overlaps in frequency with abroadcast control channel or signal, and a second set of sCCEs if noneof the RBs of the set of RBs overlap in frequency with a broadcastcontrol channel or signal, wherein the first and the second set of sCCEscan be different. The first set of sREGs can be a subset of the secondset of sREGs. The control channel candidate can comprise a set of sCCEs,and the set of sCCEs can be a first set of sCCEs if at least one RB ofthe set of RBs can at least partially overlaps in frequency with abroadcast control channel or signal, and a second set of sCCEs if noneof the RBs of the set of RBs can overlap in frequency with a broadcastcontrol channel or signal, wherein the first and the second set of sCCEsare different.

The second set of sCCEs can be a subset of the first set of sCCEs. Thecontroller 2120 can monitor the control channel using DMRS's in the atleast sTTI. At least a subset of the set of sREGs can be use a DMRS onan AP, where a single-layer precoder can apply to all DMRS REs in the atleast subset of the set of sREGs.

The at least one sTTI can comprises one of a first two sTTIs in a secondslot of a subframe. RBS containing synchronization signals can beexcluded from being included in the mapping of control resources insTTIs overlapping with synchronization signals in the time domain. Atleast one RB of the set of RBs comprises synchronization signals, the REin the at least one RB of the set of RBs can be excluded from being usedfor determining control REs for the control channel candidate in the atleast one sTTI overlapping with the synchronization signals in the timedomain.

In yet another possible embodiment, the transceiver 2170 can transmit ahigher layer message indicating to monitor a control channel using DMRSin a sTTI in a subframe, where the higher layer can be higher than aphysical layer, and where the sTTI can be shorter than a subframe-lengthTTI. The transceiver 2170 can further transmit a first control channelcandidate in the sTTI, where the first control channel candidate cancomprise a first sCCE spanning a first set of sREGs in a frequencydomain using a first DMRS on a first AP. A first precoder can apply toall DMRS REs in the first set of sREGs, where the sREG corresponds tothe sTTI. The transceiver 2170 can further transmit a second controlchannel candidate in the sTTI, where the second control channelcandidate can comprise a second sCCE spanning a second set of sREGs inthe frequency domain using a second DMRS on a second AP, where a secondprecoder can apply to all DMRS REs in the second set of sREGs, wherein afirst sREG of the first set of sREGs can occupy a first set of REs in agiven RB in a first OFDM symbol and a second sREG of the second set ofsREGs can occupy a second set of REs, in the given RB in a second OFDMsymbol. The first OFDM symbol can be different from the second OFDMsymbol.

According to a possible embodiment, some sREGs in the first set of sREGs(sCCE1) occupy same RBs in both the first OFDM symbol and the secondOFDM symbol and another sREG in the first set of sREGs (sCCE1) for thegiven RB occupying only one OFDM symbol. For example, referring to FIG.12, a first set of sREGs (sCCE1) can occupy REs in RB1, sym 0 and asecond set of sREGs (sCCE2) can occupy REs in RB1, sym 1. According to apossible embodiment, the control candidates can include one or moreCCEs. According to a possible embodiment, the number of PRBs in a sCCEcan be the same for each sCCE. According to a possible embodiment, acontrol channel can be a sPDCCH and the flowcharts can be performed bythe UE 110.

According to a possible embodiment, a precoding granularity of aprecoder for the first sCCE can comprise multiple RBs in the frequencydomain that are equal to the number resource blocks in the first OFDMsymbol. The precoding granularity can be based on Precoder Resourceblock Group (PRG) bundling. As understood to one of ordinary skill inthe art, precoder granularity of a number of PRBs can mean the sameprecoder can be provided for the number of PRBs.

According to a possible embodiment, the first control channel candidateand the second control channel candidate can each comprise a singlesCCE. For example, this can be for an aggregation level 1. A number ofsCCEs in a control channel candidate can also be based on the sCCEaggregation level. A sCCE can include 3 sREGs, such as 3 RBs. Accordingto a possible embodiment, the first AP can be used for even controlchannel (sPDCCH) candidates of a size of one sCCE and the second AP canbe used for odd control channel (sPDCCH) candidates of a size of oneCCE. According to a possible embodiment, the first AP can be furtherbased on a UE Identifier (ID). For example, the UE ID can equate to aUser Equipment Identifier, such as Cell-RNTI (C-RNTI). According to apossible embodiment, the first AP can be further based on an index ofthe first sCCE.

In a possible embodiment, the higher layer message can be a first higherlayer message, the sTTI can be a first sTTI, and the subframe can be afirst subframe, 1700 can further comprise receiving a downlink signalfrom the base station, determining a number of CRS APs based on thereceived downlink signal, receiving a second higher layer message tomonitor a third control channel candidate using DMRS's in at least onesTTI in a second subframe, where the second higher layer can be higherthan a physical layer. 1700 can further include determining whether tomonitor the third control channel candidate using DMRS's in a secondsTTI of the at least one sTTI based on the determined number of CRS APsin response to receiving the second higher layer message and attemptingto decode the third control channel candidate using a third DMRS in thesecond sTTI if it can be determined to monitor the control channelcandidate using DMRS in the second sTTI.

In a possible embodiment, control symbols in the sTTI can overlap with aCRS containing symbol. 1700 can further include determining to excludemonitoring of a sPDCCH using given DMRS's in the sTTI of the sTTI whenthe determined number of CRS APs can be larger than a threshold numberof APs.

In a possible embodiment, the transceiver 2170 can transmit a higherlayer message from a base station for monitoring control channelcandidates in at least one sTTI in a subframe and a set of RBscorresponding to control channel candidates in the at least one sTTI,can be received, where the higher layer can be higher than a physicallayer, and where a sTTI can be shorter than a subframe-length TTI. Thecontroller 2120 can determine whether at least one RB of the set of RBsat least partially overlaps with a broadcast control channel or signal.The controller 2120 can attempt decoding of the control channelcandidate in the at least one sTTI according to the determined controlresource REs, where the control channel candidate can comprise an sCCEspanning a set of sREGs in a frequency domain.

According to a possible embodiment, the controller 2120 can use a firstmapping to map control information to control resource REs used fortransmission of the control channel candidate if at least one RB of theset of RBs at least partially overlaps in frequency with a broadcastcontrol channel or signal, and can use a second mapping to map controlinformation to control resource REs used for transmission of the controlchannel candidate if none of the RBs of the set of RBs overlap infrequency with a broadcast control channel or signal, wherein the firstand the second mappings are different.

In an example, the controller 2120 can excluded the control informationfrom being mapped to the at least one RB of the set of RBs that at leastpartially overlaps with the broadcast control channel or signal. In anexample, control information can be excluded from being mapped to asecond set of RBs if the at least one RB of the set of RBs that at leastpartially overlaps with the broadcast control channel or signal belongto the second set of RBs, wherein the second set of RBs can be a subsetof the set of RBs. In an example, the second set of RBs can form aresource block group (RBG), where an RBG can be a unit of schedulingdownlink data transmissions. In an example, the RBG size can be largerthan 6 RBs.

According to a possible embodiment, the set of sREGs of the sCCE can bea first set of sREGs if at least one RB of the set of RBs at leastpartially overlaps in frequency with a broadcast control channel orsignal. According to a possible embodiment, a second set of sREGs ifnone of the RBs of the set of RBs overlap in frequency with a broadcastcontrol channel or signal. In an example, the first and the second setof sREGs can be different. In an example, the first set of sREGs can bea subset of the second set of sREGs.

According to a possible embodiment, the control channel candidate cancomprise a set of sCCEs, and the set of sCCEs can be a first set ofsCCEs if at least one RB of the set of RBs at least partially overlapsin frequency with a broadcast control channel or signal, and can be asecond set of sCCEs if none of the RBs of the set of RBs overlap infrequency with a broadcast control channel or signal. In an example, thefirst and the second set of sCCEs can be different. In a possibleembodiment, the at least one sTTI can comprise one of a first two sTTIsin a second slot of a subframe. In a possible embodiment, RBs containingsynchronization signals can be excluded from being included in themapping of control resources in sTTIs overlapping with synchronizationsignals in the time domain.

Moreover, a further possible embodiment can include an apparatus andmethod that can include the transceiver 2170 to receive a higher layermessage from a base station, for monitoring sPDCCH control channel usingDMRS in a plurality of sTTIs in a subframe, where the higher layer canbe higher than a physical layer, and where the sTTI can be shorter thana subframe-length TTI and attempting to decode sPDCCH using DMRS in afirst sTTI wherein at least one control symbol in the first sTTI can beexcluded from overlap with a CRS containing symbol. The apparatus andmethod can further include the controller 2120 to attempt to decodesPDCCH using DMRS in a second sTTI using DM-RS REs present in the firstsTTI, wherein at least one control symbol in the second sTTI can overlapat least partially with a CRS containing symbol, and the second sTTI canbe adjacent to the first sTTI. The apparatus can be the UE 110 and themethod can be performed by the UE 110. In an example, DMRS-based sPDCCHcan happen in sTTI “n” including CRS, or sTTIs wherein the controlsymbols overlap for DMRS-based sPDCCH with a CRS containing symbol, onlywhen the DMRS can be shared between sTTI “n−1” and sTTI “n” and presentin sTTI “n−1”. In an example, the UE 110 can assume no DM-RS can betransmitted for sPDCCH candidates in sTTI n and can use the DM-RS REsfrom sTTI n−1 for demodulation of sPDCCH candidates in sTTI n. In anexample, the UE 110 can use the same subcarriers for DM-RS in sTTI n−1for attempting to decode sPDCCH in sTTI n as would be the case if DM-RSwas transmitted on sTTI n. In an example, the DM-RS from sTTI n−1 can atleast overlap in frequency with the sREGs associated with the sPDCCH insTTI n. If the UE 110 can be configured to monitor, via the controller2120, DMRS-based sPDCCH, the UE 110 can monitor the DMRS-based sPDCCH inan sTTI containing CRS, or sTTIs wherein the control symbols overlapwith a CRS containing symbol, assuming DMRS can be shared between theprevious sTTI and the current sTTI. In such a case, still the AL orlocation of the control might be different between the sTTIs sharing theDMRS, but the control resources of the second sTTI can fully overlappedwith control and data resources of the first sTTI containing the DMRS.In an example, the second sTTI can follow the first sTTI.

In a possible embodiment, for example the transceiver 2170 can receive ahigher layer message from a base station for monitoring control channelcandidates in at least one sTTI in a subframe and set of RBscorresponding to control channel candidates in the at least one sTTI,where the higher layer can be higher than a physical layer, and where asTTI can be shorter than a subframe-length TTI. The controller 2120 candetermine a higher layer message from a base station for monitoringcontrol channel candidates in at least one sTTI in a subframe and set ofRBs corresponding to control channel candidates in the at least onesTTI, where the higher layer can be higher than a physical layer, andwhere a sTTI can be shorter than a subframe-length TTI and determinecontrol resource REs used for transmission of a control channelcandidate based on the determining whether at least one RB of the set ofRBs at least partially overlaps in frequency with a broadcast controlchannel or signal. The controller 2120 can attempt to decode the controlchannel candidate in the at least one sTTI according to the determinedcontrol resource REs, wherein the control channel candidate comprises ansCCE spanning a set of sREGs in a frequency domain, the set of shortenedresource elements groups comprising the determined control resourceelements.

According to a possible embodiment, the controller 2170 can use a firstmapping to map control information to control resource REs used fortransmission of the control channel candidate if at least one RB of theset of RBs at least partially overlaps in frequency with a broadcastcontrol channel or signal, and use a second mapping to map controlinformation to control resource REs used for transmission of the controlchannel candidate if none of the RBs of the set of RBs overlap infrequency with a broadcast control channel or signal, wherein the firstand the second mappings can be different. The second set of sCCEs can bea subset of the first set of sCCEs.

In an example, the controller 2170 can exclude control information frombeing mapped to the at least one RB of the set of RBs that at leastpartially overlaps with the broadcast control channel or signal. In anexample, control information can be excluded from being mapped to asecond set of RBs if the at least one RB of the set of RBs that at leastpartially overlaps with the broadcast control channel or signal belongto the second set of RBs, wherein the second set of RBs can be a subsetof the set of RBs. In an example, the second set of RBs can form aresource block group (RBG), where an RBG can be a unit of schedulingdownlink data transmissions. In an example, the RBG size can be largerthan 6 RBs.

According to a possible embodiment, the set of sREGs of the sCCE can bea first set of sREGs if at least one RB of the set of RBs at leastpartially overlaps in frequency with a broadcast control channel orsignal. According to a possible embodiment, a second set of sREGs ifnone of the RBs of the set of RBs overlap in frequency with a broadcastcontrol channel or signal. In an example, the first and the second setof sREGs can be different. In an example, the first set of sREGs can bea subset of the second set of sREGs.

According to a possible embodiment, the control channel candidate cancomprise a set of sCCEs, and the set of sCCEs can be a first set ofsCCEs if at least one RB of the set of RBs at least partially overlapsin frequency with a broadcast control channel or signal, and can be asecond set of sCCEs if none of the RBs of the set of RBs overlap infrequency with a broadcast control channel or signal. In an example, thefirst and the second set of sCCEs can be different. According to apossible embodiment, the controller 2170 can further monitor the controlchannel using DMRS's in the at least sTTI. In an example, the set ofsREGs can use a DMRS on an AP, where a precoder applies to all DMRS REsin the set of sREGs. In a possible embodiment, the at least one sTTI cancomprise one of a first two sTTIs in a second slot of a subframe. In apossible embodiment, the controller 2170 can exclude RBs containingsynchronization signals from being included in the mapping of controlresources in sTTIs overlapping with synchronization signals in the timedomain.

Additionally, another further possible embodiment can include anapparatus and method that can include receiving a first higher layermessage for monitoring a control channel candidate using CRS in at leastone sTTI in a subframe, where the higher layer can be higher than aphysical layer and receiving a second higher layer message indicatingwhether the control channel candidate in the at least one sTTI can bemapped to a first set of DMRS REs in control resources of the controlchannel candidate. The apparatus and method can further includeattempting to decode the control channel candidate using CRS in the atleast one sTTI based on the received second higher layer message whenmonitoring the control candidates. The apparatus can be the UE 110 andmethod can be performed by the UE 110. For example, the sPDCCH in the atleast one sTTI can be rate-match around data DMRS REs in the sPDCCHcontrol resources. In an example, the first set of DMRS REs can beassociated with a downlink data transmission mode configured for the UE110. In an example, the apparatus and method can further includereceiving a third higher layer message indicating a number of controlsymbols for a control channel candidate using CRS and indicating theposition of at least one control symbol in the at least one sTTI. In anexample, the at least one sTTI comprises one or more symbols containingCRS, and the position of a control symbol for a sPDCCH in the at leastone sTTI can be other than the position of at least one symbolscontaining CRS. In an example, a third sREG of the first set of sREGs(sCCE1) occupies a third set of REs in a given RB in the first OFDMsymbol, such as REs in RB1, sym 0 illustrated in FIG. 12, and the firstcontrol candidate can be excluded from occupying REs in the given RB inthe second OFDM symbol, except DMRS REs associated with the third sREG.In an example, the DMRS REs in the first and the second OFDM symbolsassociated with the third sREG can be determined based on at least thefrequency location of DMRS REs corresponding to downlink datatransmissions of a downlink data transmission mode.

The method of this disclosure can be implemented on a programmedprocessor. However, the controllers, flowcharts, and modules may also beimplemented on a general purpose or special purpose computer, aprogrammed microprocessor or microcontroller and peripheral integratedcircuit elements, an integrated circuit, a hardware electronic or logiccircuit such as a discrete element circuit, a programmable logic device,or the like. In general, any device on which resides a finite statemachine capable of implementing the flowcharts shown in the figures maybe used to implement the processor functions of this disclosure.

While this disclosure has been described with specific embodimentsthereof, it is evident that many alternatives, modifications, andvariations will be apparent to those skilled in the art. For example,various components of the embodiments may be interchanged, added, orsubstituted in the other embodiments. Also, all of the elements of eachfigure are not necessary for operation of the disclosed embodiments. Forexample, one of ordinary skill in the art of the disclosed embodimentswould be enabled to make and use the teachings of the disclosure bysimply employing the elements of the independent claims. Accordingly,embodiments of the disclosure as set forth herein are intended to beillustrative, not limiting. Various changes may be made withoutdeparting from the spirit and scope of the disclosure.

In this document, relational terms such as “first,” “second,” and thelike may be used solely to distinguish one entity or action from anotherentity or action without necessarily requiring or implying any actualsuch relationship or order between such entities or actions. The phrase“at least one of,” “at least one selected from the group of,” or “atleast one selected from” followed by a list is defined to mean one,some, or all, but not necessarily all of, the elements in the list. Theterms “comprises,” “comprising,” “including,” or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus. An element proceeded by “a,” “an,” or the like does not,without more constraints, preclude the existence of additional identicalelements in the process, method, article, or apparatus that comprisesthe element. Also, the term “another” is defined as at least a second ormore. The terms “including,” “having,” and the like, as used herein, aredefined as “comprising.” Furthermore, the background section is writtenas the inventor's own understanding of the context of some embodimentsat the time of filing and includes the inventor's own recognition of anyproblems with existing technologies and/or problems experienced in theinventor's own work.

We claim:
 1. A method, comprising: receiving, by a device, a higherlayer message from a base station indicating to monitor a controlchannel using demodulation reference signals in a shortened transmissiontime interval in a subframe, where the higher layer is higher than aphysical layer, and where the shortened transmission time interval isshorter than a subframe-length transmission time interval; attempting todecode a first control channel candidate in the shortened transmissiontime interval, where the first control channel candidate comprises afirst shortened control channel element spanning a first set ofshortened resource element groups in a frequency domain using a firstdemodulation reference signal on a first antenna port, where a firstprecoder applies to all demodulation reference signal resource elementsin the first set of shortened resource element groups, where theshortened control channel element corresponds to the shortenedtransmission time interval; and attempting to decode a second controlchannel candidate in the shortened transmission time interval, where thesecond control channel candidate comprises a second shortened controlchannel element spanning a second set of shortened resource elementgroups in the frequency domain using a second demodulation referencesignal on a second antenna port, where a second precoder applies to alldemodulation reference signal resource elements in the second set ofshortened resource element groups, wherein a first shortened resourceelement group of the first set of shortened resource element groupsoccupies a first set of resource elements in a given resource block in afirst orthogonal frequency division multiplexing symbol of the shortenedtransmission time interval and a second shortened resource element groupof the second set of shortened resource element groups occupies a secondset of resource elements, in the given resource block in a secondorthogonal frequency division multiplexing symbol of the shortenedtransmission time interval, where the first orthogonal frequencydivision multiplexing symbol is different from the second orthogonalfrequency division multiplexing symbol.
 2. The method according to claim1, wherein some shortened resource element groups in the first set ofshortened resource element groups occupy same resource blocks in boththe first orthogonal frequency division multiplexing symbol and thesecond orthogonal frequency division multiplexing symbol and anothershortened resource element group in the first set of shortened resourceelement groups for the given resource block occupying only oneorthogonal frequency division multiplexing symbol.
 3. The methodaccording to claim 1, wherein a precoding granularity of the firstprecoder for the first shortened control channel element comprisesmultiple resource blocks in the frequency domain that are equal to thenumber resource blocks in the first orthogonal frequency divisionmultiplexing symbol.
 4. The method according to claim 1, wherein thefirst and the second control channel candidates each comprises a singleshortened control channel element.
 5. The method according to claim 1,wherein the first antenna port is used for even control channelcandidates of a size of one shortened control channel element and thesecond antenna port is used for odd control channel candidates of a sizeof one shortened control channel element.
 6. The method according toclaim 1, wherein the first antenna port is further based on a userequipment identifier.
 7. The method according to claim 1, wherein thefirst antenna port is further based on an index of the first shortenedcontrol channel element.
 8. The method according to claim 1, wherein thehigher layer message is a first higher layer message, the shortenedtransmission time interval is a first shortened transmission timeinterval, and the subframe is a first subframe, the method furthercomprising: receiving a downlink signal from the base station;determining a number of cell-specific reference signal antenna portsbased on the received downlink signal; receiving a second higher layermessage to monitor a third control channel candidate using demodulationreference signals in at least one shortened transmission time intervalin a second subframe, where the second higher layer is higher than aphysical layer; determining whether to monitor the third control channelcandidate using demodulation reference signals in a second shortenedtransmission time interval of the at least one shortened transmissiontime interval based on the determined number of cell-specific referencesignal antenna ports in response to receiving the second higher layermessage; and attempting to decode the third control channel candidateusing a third demodulation reference signal in the second shortenedtransmission time interval if it is determined to monitor the controlchannel candidate using DMRS in the second shortened transmission timeinterval.
 9. The method according to claim 1, wherein control symbols inthe shortened transmission time interval overlap with a cell-specificreference signal containing symbol, and wherein the method furthercomprises determining to not monitor a shortened physical downlinkcontrol channel using given demodulation reference signals in theshortened transmission time interval of the shortened transmission timeinterval when the determined number of cell specific reference signalantenna ports is larger than a threshold number of antenna ports.
 10. Anapparatus, comprising: a transceiver to receive a higher layer messagefrom a base station indicating to monitor a control channel usingdemodulation reference signals in a shortened transmission time intervalin a subframe, where the higher layer is higher than a physical layer,and where the shortened transmission time interval is shorter than asubframe-length transmission time interval; wherein the apparatusattempts to decode a first control channel candidate in the shortenedtransmission time interval, where the first control channel candidatecomprises a first shortened control channel element spanning a first setof shortened resource element groups in a frequency domain using a firstdemodulation reference signal on a first antenna port, where a firstprecoder applies to all demodulation reference signal resource elementsin the first set of shortened resource element groups, where theshortened control channel element corresponds to the shortenedtransmission time interval, wherein the apparatus attempts to decode asecond control channel candidate in the shortened transmission timeinterval, where the second control channel candidate comprises a secondshortened control channel element spanning a second set of shortenedresource element groups in the frequency domain using a seconddemodulation reference signal on a second antenna port, where a secondprecoder applies to all demodulation reference signal resource elementsin the second set of shortened resource element groups, and wherein afirst shortened resource element group of the first set of shortenedresource element groups occupies a first set of resource elements in agiven resource block in a first orthogonal frequency divisionmultiplexing symbol and a second shortened resource element group of thesecond set of shortened resource element groups occupies a second set ofresource elements, in the given resource block in a second orthogonalfrequency division multiplexing symbol, where the first orthogonalfrequency division multiplexing symbol is different from the secondorthogonal frequency division multiplexing symbol.
 11. The apparatusaccording to claim 10, wherein some shortened resource element groups inthe first set of shortened resource element groups occupy same resourceblocks in both the first orthogonal frequency division multiplexingsymbol and the second orthogonal frequency division multiplexing symboland another shortened resource element group in the first set ofshortened resource element groups for the given resource block occupyingonly one orthogonal frequency division multiplexing symbol.
 12. Theapparatus according to claim 10, wherein a precoding granularity of thefirst precoder for the first shortened control channel element comprisesmultiple resource blocks in the frequency domain that are equal to thenumber resource blocks in the first orthogonal frequency divisionmultiplexing symbol.
 13. The apparatus according to claim 10, whereinthe first and the second control channel candidates each comprises asingle shortened control channel element.
 14. The apparatus according toclaim 10, wherein the first antenna port is used for even controlchannel candidates of a size of one shortened control channel elementand the second antenna port is used for odd control channel candidatesof a size of one shortened control channel element.
 15. The apparatusaccording to claim 10, wherein the first antenna port is further basedon a user equipment identifier.
 16. The apparatus according to claim 10,wherein the first antenna port is further based on an index of the firstshortened control channel element.
 17. The apparatus according to claim10, wherein the higher layer message is a first higher layer message,the shortened transmission time interval is a first shortenedtransmission time interval, and the subframe is a first subframe,wherein the apparatus further receives a downlink signal from the basestation, wherein the apparatus further determines a number ofcell-specific reference signal antenna ports based on the receiveddownlink signal, wherein the apparatus further receives a second higherlayer message to monitor a third control channel candidate usingdemodulation reference signals in at least one shortened transmissiontime interval in a second subframe, where the second higher layer ishigher than a physical layer, wherein the apparatus further determineswhether to monitor the third control channel candidate usingdemodulation reference signals in a second shortened transmission timeinterval of the at least one shortened transmission time interval basedon the determined number of cell-specific reference signal antenna portsin response to receiving the second higher layer message, and whereinthe apparatus further attempts to decode the third control channelcandidate using a third demodulation reference signal in the secondshortened transmission time interval if it is determined to monitor thecontrol channel candidate using DMRS in the second shortenedtransmission time interval.
 18. The apparatus according to claim 10,wherein control symbols in the shortened transmission time intervaloverlap with a cell-specific reference signal containing symbol, andwherein the apparatus further determines to not monitor a shortenedphysical downlink control channel using given demodulation referencesignals in the shortened transmission time interval of the shortenedtransmission time interval when the determined number of CRS antennaports is larger than a threshold number of antenna ports.